Firebase orderByPriority used with equalTo strange behavior - firebase

Question

I try to use the second argument of equalTo(value, key) when using orderByPriority(), as documented here.
The problem is that results are inconsistent when using that second key argument.
Example dataset
items
key1
key2
key3
key4
All items have the same priority: 10 (this is just for the example, in my app there are other items with other priorities)
When issuing the following Firebase query to get the first two items with that priority:
dbRef.child('items').orderByPriority().equalTo(10).limitToFirst(2)
I get the following - expected - results :
{ "key1": ..., "key2": ... }
Then I try to get the results after the key2 item, as explained in the docs:
dbRef.child('items').orderByPriority().equalTo(10, 'key2').limitToFirst(2)
Result is pretty strange, with always only one item, the one with the provided key:
{ "key2": ... }
What i was expecting is two results starting at or after the key provided, so
{ "key2": ..., "key3": ... }
Or
{ "key3": ..., "key4": ... }
Question
How should I use the equalTo() filter with its second argument?
It seem this question was already asked, but it did not get any answers...

Answer 1

The equalTo() filter will only get items exactly matching the key specified. If you'd like to start at 'key2' and get multiple after that, use the startAt() filter. You cannot use multiple orderBy statements in the same query, though, so you may need to reformat your code. I would recommend that you save items by desired priority. Then you can query that group of items using the startAt() filter. Heres a dataset:
items10
key1
key2
items9
key1
key2
In the startAt() filter, you specify the starting key, and then it will query for any key with the same or greater value. Here's a link to the docs for this functionality: startAt().
Using this method, limitToFirst(2) should give you key2 and key3. Here's a code example, using priority 10.
dbRef.child('items10').orderByKey().startAt('key2').limitToFirst(2)
Note: you may also need to just grab an element, without knowing its priority. For this, create another key called items that just contains all keys (you would not use this for queries).